@mitu Is the Retroarch version the number shown in the bottom left corner of RGUI, along with the currently loaded core? If so, mine is on 1.8.8 somehow. If not, where can I check my current RA version?

Yeah, so I now updated to RA version 1.10 (d'oh) and I can see the menu entries in the aforementioned places.

Setting turbo mode to single button (hold) and turbo default button to X (my preferred button) still doesn't make it work as I intend. For instance, 1944 still charges up a shot when holding down the button instead of rapid firing. single button (toggle) does work as I would expect it to, though.

What am I doing wrong?

EDIT: Okay, got it. After updating RA, if I put

input_turbo_period = "6" input_duty_cycle = "3" input_turbo_mode = "2" input_turbo_default_button = "0" input_player1_turbo_btn = "3"

into my cfg file, button 3 does function as a turbo button, WITHOUT modulating any other buttons, so I guess the previously linked post was correct after all, I was just rocking an older version and didn't realize it.

Thanks to all respondents for bearing with me!

Mame buttons turbo delay